class Animal(object):
    def eat(self):
        print("eating...")

    def sleep(self):
        # print("self...", id(self))
        print("sleeping...")

class Dog(Animal):
    def swimming(self):
        print("swimming...")

alex = Dog()

class Fly(object):
    def fly(self):
        print("fly...")

class Eagle(Animal, Fly):
    pass

class Bat(Animal, Fly):
    pass

b1 = Bat()
b1.fly()

e1 = Eagle()
e1.fly()

